Treating petroleum distillates



Patented May 8, 1951 2,552,399 TREATING PETROLEUM DISTILLATES- John G. Browder, Houston, Tex., assignor, by mesne assignments, to Standard Oil Development Company, Elizabeth, N. J., a corporation of Delaware No Drawing. Application February 19, 1949,

Serial No. 77,447

4 Claims. (Cl. 196-29) 1 2 The present invention is directed to a method provide an improved sweetening process in which for treating sour petroleum distillates. More par small amounts of catalytic reagents are emticularly, the invention is directed to the sweetenployed. ing of sour petroleum distillates in the presence In the foregoing discussion of the prior art, it of an alkali metal hydroxide and a mild oxidizing 6 will be seen that the prior art workers added agent. 7 compounds such as phenols and amines to the Prior to the present invention, it has been alkaline solutions which were employed to treat known to treat sour petroleum distillates with sour petroleum distillates. I have now found aqueous alkaline solutions, such as solutions of that, in distinction to the prior art workers, imalkali metal hydroxide, to remove hydrogen sul- 10 proved results may be obtained by adding catafide and other acidic bodies, following which the lytic amounts of a benzenoid compound selected sour distillates were treated with sodium plumfrom the group consisting of the amines and bite solution to convert deleterious sulfur comphenols to the sour petroleum distillate rather pounds to compounds which are largely innocuthan to the alkaline solution. Therefore, in acous. This and other prior art processes relied l5 cordance with the present invention, the foreon the addition of sulfur to cause the conversion going objects may be obtained by adding to sour of the sulfur compounds from mercaptans to dipetroleum distillates a catalytic amount of a sulfides. Other processes convert the undesirable benzenoid compound selected from the groups compounds by means of lead sulfide, which is consisting of phenols and amines and then conthen separated from the gasoline. Frequently, tacting the sour distillate containing the subthe separation of lead sulfide from the gasoline tit ted n en d Compound With a y Small was not complete, and, consequently, some was catalytic quantity of a solution of an alkali metal carried over into storage, which was disadvanhydroxide while maintaining in contact theretageous. Furthermore, the addition of sulfur with a ild oXidiZing agent to gasoline frequently impaired the octane num- Accordingly, it may be seen that the present her level of the gasoline since it is well known invention may be described briefily as involving that sulfur and its compounds affect gasoline treating a sour petroleum distillate boiling in the detrimentally. range from about 50 to 750 F. by contacting the Efiorts have been made in the prior art to distillate with a solution of an alkali metal hy-, remedy this situation, and the workers in the droxide while maintaining in the sour distillate field have turned to adding certain compounds, a catalytic amount of a benzenoid compound sesuch as phenols and amines, to alkaline solulected from the group consisting of the amines tions, such as sodium hydroxide, to cause converand phenols and adding to the contacted mix-; sion through an oxidation mechanism of the dew ture a mild oxidizing agent sufficient to sweeten leterious compounds in the sour naphtha. Fr,esaid distillate, following which the alkali metal quently such expedients are unsatisfactory in not hydroxide is separated from the contacted discompletely sweetening the product and an aftertillate.; treatment, by one of the well known sweetening The benzenoid compounds from the group conprocedures, becomes necessary. 7 sisting of amines and phenols, which find use'in- From the foregoingdiscussion of the prior art, 46 the present invention, may be illustrated by hyit will be seen that the petroleum refining indusdroquinone, cresols, catechol, pyrogallol, xyletry has been faced with a problem of converting nols, crude petroleum phenols, tertiary amyl deleterious sulfur compounds present in petrophenol, phenol, beta naphthol, amino-phenols: leum distillates to those which do not detrimensuch as p-amino phenol, the phenylenediamines tally affect the quality of the product. such as ortho, meta, and paraphenylene-diamine, i

It is, therefore, the main object of the present N,N'-di-sec-butyl-p-phenylenediamine, and othinvention to provide a treating process in which er amines and phenols. improved results are obtained in converting ob-- These compounds may be employed in amounts,'- jectionable sulfur compounds to harmless bodies. based on the naphtha, varying from 0.001 to 1.0

Another object of the present invention is to 50 per cent by volume, with a preferred range from T p e an p ed W e n process in which about 0.01 to 0.15 per cent by volume. It is to be] an active material is added to the petroleum disemphasized that the specified amount of the tillate being sweetened to catalyze the conversion benzenoid compound selected from the group conof d t s s lfu mp unds. sisting of the amines and phenols should be added Another object of the present invention is to i to the naphtha and not-to the alkaline solution.

The alkaline solution employed in the present invention should be a solution of an alkali metal hydroxide. Preferably the solution should be an aqueous solution having a Baum gravity in the range from about 30 to 50 B. but solutions of lower strengths may be used under some conditions. For example, a 40 B. aqueous solution of sodium hydroxide gives satisfactory results.

The alkali metal hydroxide may be lithium, sodium, or potassium hydroxide, but sodium hydroxide will be preferred on acount .of'ii-tsiavailability.

The temperature at which the .trea tingoperation is conducted will usually be atmospheric temperature and may range'from about 60F. up to about 200 F. and sometimes higher depending on the boiling range and type :of'the sto'ck being treated. A preferred temperature range will be from about 70 to about 95 F. Satisfactory :results have been obtainedat atmospheric temperatures encountered in the Texas Gulf Coast area.

The present invention will be further illustrated-by the following examples.

EXAMPLE I A hydrogen su'lfide'free high sulfur petroleum -distillate boiling in the kerosene boiling range, having a coppernumber of 4l,'was divided into three portions. Gne portion was treated by contacting with 5% by volume of 40 B. sodium hydroxide solution in the presence of 3 times the theoretical amount of oxygen required to sweeten the naphtha. The second portion was contacted with 5% by volume of 40 B. sodium hydroxide solution to which had been added 0.1% by volume of "crude petroleum phenolsbased on the naphtha. This treatment was also conducted in the presence of 3 times the theoretical amount of oxygen necessary to sweetent the naphtha. The third portion had added to it 0.1% by weight of crude petroleum phenols based on the naphtha and then was contacted with 1% by volume of 40 B. caustic in the presence of 3 times the theoretical amount of oxygen required to "sweeten. The copper numbers of the three treated samples were then tested immediately and after 1, 5, and 22 hours settling time. The results of these tests are presented in Table I in which the first column shows the treatment with 40 'B. caustic; the second column gives the results on the portion treated with sodium hydroxide containing petroleum phenols; and the third column gives results of the portion treated in accordance with the present invention.

Table I Copper No. of N-aphtha Aftersettling For, Hours 1 .2

eat;

treated in accordance with the present invention had its copper number reduced from 41 to 18 which after 1 hour had dropped to 11 and after 5 hours to 4 and after 22 hours to a 0 copper number and also was found to pass the wall known doctor test. These results conclusively :demonstrate that adding the petroleum phenols to the naphtha rather than to the sodium hydroxide allows vastly improved results with smaller amounts of reagent than was possible .iheretofore.

.EXAlVIPLE II .In this .run .a portion of hydrogen sulfide free kerosene having a copper number of 52 was divided into four portions. One portion was con ta'cted with 5% by volume of 40 Be. sodium hydroxide solution and contacted with 300% of the theoretical amount of oxygen required to sweeten. The second portion was contacted with 5% by volume of 40 B. sodium hydroxide which was saturated with petroleum phenols, and also contacted with-300% of the theoretical amount of oxygen required to sweeten. The third portion had added to the kerosene .approximately 0.003% by volume of N,N'-di-sec- ,butyl-p-phenylenediamine whereas the fourth portionhad added to jit 0.01% 'by volume of LEN- ..di secbutyl-p-phenylenediamine. These .two portions were then treated in contact with 300% of the theoretical amount of oxygen with 1 and 0.6% by volume, respectively, of .asolution of 40 B. sodium hydroxide.

"The four portions treated as described were .then'tested for copper number after the treatment and afterstanding'for L3, 5., and hours. The results of these tests are shown in the following table in whichthe firsticolumn shows the treat with the sodium hydroxide solution and oxygen; the second column shows the treat with oxygen andsodium hydroxide to which had been added petroleum phenols; while the third and fourth columns illustrate the practice of the present invention with varying amounts of N,N di-sec-butyl-p-phenylenediamine, 40 Be. sodium hydroxide solution, and oxygen.

Table II Copper No. of Naphtha After Settling For, Hours 1 v2 3 4 mandamu or-uv-e:

It will be seen from the foregoing data that the treatment with "5% 40 B sodium hydroxide reduced the copper number of the stock from 52 to -.44 after .20 hours standingwhile, when the petroleum phenols were added to the caustic, the copper number was reduced after treatment from 52 to 49 and then dropped slowly after 20hours standing to 30, again which is a relatively sour present invention, the stock will slowly sweeten on standing.

EXAMPLE III In another run in accordance with the present invention, five portions of a hydrogen sulfide free low copper number catalytically cracked naphtha were obtained. One portion was contacted with 300% of the theoretical amount of oxygen to sweeten in the presence of by volume of a 40 B. sodium hydroxide solution saturated with petroleum phenols. The second portion was also contacted with 300% of the theoretical amount of oxygen, but in this case 1% of 40 B. sodium hydroxide solution containing no petroleum phenols was employed. The third portion had added to it approximately 0.004% by volume of N,N- di-sec-butyl-p-phenylenediamine and was contacted with 300% of the theoretical amount of oxygen necessary to sweeten, in the absence of sodium hydroxide. The fourth portion had added to it approximately 0.004 by volume of N,N'-disec-butyl-p-phenylenediamine and then was contacted in the presence of 300% of the theoretical amount of oxygen required to sweeten, with 1% by volume of 40 B. sodium hydroxide. The fifth portion was contacted similarly to the fourth portion with the difierence that no oxygen was added other than that present in the treating vessel.

The naphtha, after the foregoing treatments, were tested for copper number immediately after the treat and after standing 1, 3, 5, 20, and 70 hours. The results of these tests are presented in the following table in which the first column.

gives the results of the tests on the naphtha treated with oxygen and with caustic to which had been added the petroleum phenols. The second column presents the results of the tests on the naphtha treated with 1% by volume of caustic and oxygen, while the third column gives the results on the naphtha to which had been added approximately 0.004% by volume of N,N'-di-secbutyl-p-phenylenediamine and treated with 300% of the theoretical amount of oxygen required to sweeten in the abosence of caustic. The fourth column presents data on the process of the present invention in which the N,N'-disec-butyl-p-phenylenediamine was added to the naphtha and 300% of the theoretical amount of oxygen employed in the presence of 40 B. caus-' tic to sweeten. In the fifth column giving data on a process in accordance with the present invention, the only oxygen employed was that present in the treating reagent.

Table III Copper Number After Reacting For 1 2 3 4 5 OHour 1.0 2.0 3.0 v2 2 1.0 2.0 3.0 0 0 l. 0 2. 0 3.0 Passes Passes 1. 0 2. 0 3. 0 Doctor Doctor 1.0 2.0 3.0 Test Test 1.0 2.0 3.0

be noted, however, that sweetening was not obtained when crude petroleum phenols were .added to the caustic, nor when the N,N'-di-sec-butyl-pphenylenediamine was added to the naphtha and the naphtha contacted with oxygen in the absence of sodium hydroxide. Similarly, when no N,N'- sec-butyl-p-phenylenediamine was added to the naphtha and the naphtha was contacted with the sodium hydroxide in the presence of 300% by volume of the theoretical amount of oxygen required for sweetening, sweetening was not obtained. It will be seen, therefore, that it is necessary to add the substituted benzenoid compound selected from the group consisting of the amines and phenols to the naphtha and then contact the naphtha containing the benzenoid compound with oxygen and caustic. Adding a substituted benzenoid compound to the sodium hydroxide solution is not eifective and neither is the adding of N,Ndi-sec-butyl-l-phenylenediamine to the naphtha efiective in the absence of the sodium hydroxide. It is believed significant that complete sweetening was obtained in accordance with the present invention after one hour whereas after '70 hours complete sweetening was not obtained in the prior art processes.

EXAMPLE IV In this example, a hydrogen sulfide free kerosene which was a solvent raffinate having a copper number of 50 and. a Saybolt color of 20, was divided into two parts. To one part was added 0.05% by volume of hydroquinone and the mixture was then agitated for two minutes in an agitator equipped with paddles operating at 1200 revolutions per minute, in the presence of three times the theoretical amount of oxygen, with 5% by volume, based on the kerosene, of 40 B. sodium hydroxide. The second portion was contacted with 15% B. sodium hydroxide solution to which had been added 0.05% by volume, based on the kerosene, of hydroquinone and then was agitated violently for two minutes in an agitator equipped with paddles operating at 1200 revolutions per minute in the presence of three times the theoretical amount of oxygen required to sweeten. The two treated kerosenes were separated from the caustic solutions and then tested for copper number with the results appearing in Table IV in which the data in column 1 represent the treatment in accordance with the present invention in which the hydroquinone was added to the kerosene and the data in column 2 represents the prior art method in which the hydroquinone was added to the dilute sodium hydroxide.

Table IV Copper No l Immediately After 1 Hour After 3 Hours. Alter 24 Hours prior art techniques in which the hydroquinone was added to the sodium hydroxide solution.

EXANLPLE V In this example a hydrogen sulfide free kerosene, which was a solvent raflinate having a.

7 copper number of 40, was divided into -6 parts. One-apart "was contacted with 1% of 50 B. so-

dium hydroxide solution in an agitator equipped with paddles operating at 1200 revolutions per minute for two minutes, the sodium hydroxide solution separated, and the copper number determined immediately and after standing for 1, 3, 5,

and 20 hours. The other five portions had added to them, respectively, beta naphthol, pyragallol, para-aminol phenol, tertiary amyl phenol, and phenol in an amount corresponding to 1 gram of the compound per liter of the kerosene. The live portions of kerosene containing the various compoun'ds'mentioned were then separately contacted with 1% by volume, based on the kerosene, of 50 B. sodium hydroxide solution for two minutes in an agitator equipped with paddles operating at 1200 revolutions per minute in the presence of three times the theoretical amount of oxygen required to sweeten. After the contact timespecified, the sodium hydroxide solution was separated from the five portions of kerosene and they were then tested for copper number immediately and after standing for 1, 3, 5, and 20 described herebelow. This second caustic wash was carried out similar to the first caustic wash described above; however, the 12 B. caustic solution employed, which, after settling was recycled at the rate of bbls./ hour. The naphtha efiluent from the second wash, now free of undesirable acidic compounds, was then charged to the actual sweetening step. At a first injection point in the pipe leading from the settlers to a third incorporator, 10.5 gallons/hour of crude petroleum phenols and 6.5 pounds/hour of N,N'- di-sec-butyl-p-phenylenediamine were added to the naphtha stream. At a second injection point 120 standard cubic feet per hour of oxygen (200% of the amount theoretically required to convert mercaptans present in the original charge to disulfide) was injected into the naphtha stream, and, at a third injection point 45 B. caustic, recycled from the settlers as described below, was injected at the rate of 25 bbls./hour. The mixture then passed through the third incorporator to two settlers in series, and, after a total residence time of 1 hours, the separated naphtha passed on to tankage, and the separated caustic hours. The results of these tests are shown in 25 was recycled to the injection point ahead of the Table V. third incorporator without being subjected to any Table V gem Pyrop-amino t-amyl Bcnzenoid Compound None Ntztilthganul phenol phenol phenol Cu Nm-Beforc Treat 40 40 40 40 40 40 Cu No. After Treat:

Immediately After 21 27 35 32 25 1 Hour Aftclx..- 25 21 31 31 25 3 Hours After. 28 30 20 5 Hours After. 25 25 20 Hours After 20 l0 8 1a 10 3 case, it will be seen that the treating reagent in the kerosene gave appreciably better results than when the kerosene contained no additive at all.

EXAMPLE VI In a sweetening operation in accordance with the present invention the stock treated was a naphtha comprising a mixture of virgin, catalytically cracked, thermally cracked, polymer and alkylate stocks, hydrogen sulfide, acidic bodies, and sufficient mercaptans to cause it to have a copper number of eleven. Preliminary to sweetening, this stock was subjected to a first caustic wash (aqueous sodium hydroxide) for hydrogen sulfide removal, being continuously charged at the rate of 500 bbls/hour, to an inacorporator just prior to which 5 B. caustic, at the rate of 25 bbls./hour was injected into the naphtha stream. The mixture was then allowed to settle in a system of two settlers in series, having a total residence time of 1 hours. The caustic solution drawn olf from the bottom of the settlers was recycled to the injection point ahead of the first incorporator. The naphtha efiluent from the first wash, now free of hydrogen sulfide, was then subjected to a second caustic wash for removal of undesirable acidic compounds, which degrade the uuality of the sweetened produce if allowed to remain in the stock and which also have been found to attack the amine which is addedto promote sweetening as intermediate treatment. The naphtha passing to tankage was found to have a copper number of 3.0 and after 40 hours of residence time in tankage the naphtha was found to have a zero copper number and pass the doctor test.

This particular run was continued for 36 hours, during which time the 45 B. caustic employed in the sweetening step was continuously recycled from the settlers to the injection point ahead of the incorporator at the rate of about 25 bb1s./hour without losing its effectiveness as a sweetening catalyst. No make-up caustic was required or employed. This run eifectively illustrates the catalytic action of the alkali metal hydroxide solution since it may be re-used without requiring regeneration.

In the foregoing examples, the improvement obtained in the present invention has been illustrated by the copper number test. This is a well known analytical procedure employed in the petroleum industry. A description of the method of test may be found in U. 0. P. Laboratory Test Methods for Petroleum and its Products, third edition, page 1-1-61, Universal Oil Products Company; Chicago, 1947. This test is a measure of the mercaptan sulfur content of the oil being- The invention has been illustratedby reference to the employment of petroleum phenols. This terminology has been accepted in the patent literature, The petroleum phenols may be ob tained by contacting cracked heating oil fractions boiling between 400 to 700 F., and preferably those fractions from thermal cracking operation, with a strong alkali solution, such as a 40 B. sodium hydroxide solution. This extraction causes the separation of a mixture of phenolic and naphthenic salts which may be completely acidified to release the crude petroleum phenols employed in the practice of the present invention and to illustrate the beneficial results inuring thereto. The crude petroleum phenol containing fraction may be refined to obtain purified phenolic material by modification of the above process in which the selected fraction is extracted with a 40 B. sodium hydroxide solution and the solution then partially acidified to release only the phenolic compounds, leaving the naphthenic salts in the alkaline layer. The separated phenolic compounds may be distilled to recover the desired fraction.

Although not illustrated by the several examples, one of the particular advantages of the present invention resides in the catalytic effect of the alkali metal hydroxide solution. The alkali metal hydroxide appears to function as a true catalyst since the small amount used may be recycled to treat large quantities of the sour petroleum distillate. A small amount of the alkali metal hydroxide solution may be entrained in the treated naphtha, and, therefore, it may be necessary to replace the entrained amount with fresh solution. In short, it is contemplated in the practice of the present invention that the alkali metal hydroxide solution will be reused over and over again since it is not necessary to regenerate the alkali metal hydroxide solution.

The invention has been described and illustrated by employment of a mild oxidizing agent such as oxygen. It is contemplated that mixtures of oxygen with other gases, such as air, may be employed. It is also contemplated that other mild oxidizing agents such as peroxides, permanganates, and the like may be used. For example, a hydrogen peroxide solution may be employed as the mild oxidizing agent.

In practicing the present invention, it is to be, understood that the petroleum distillate may be subjected to a preliminary treatment for removal of hydrogen sulfide if the distillate contains hydrogen sulfide. Such preliminary treatment may include washing with a dilute alkali metal hydroxide solution or blowing with a free-oxygen containing gas such as air. If hydrogen sulfide or other acidic compounds are present and not removed, the alkali metal hydroxide solution employed as the catalyst may very quickly become seriously depleted in activity.

In the practice of the invention, it will be desirable to use an amount of oxygen in excess of the theoretical required to sweeten the sour petroleum distillate. Ordinarily, an amount of about 300% of the theoretical amount to sweeten may be employed. However, sweetening in accordance with the present invention may be obtained with considerably lesser quantities of oxygen. In fact, sweetening may be obtained in some cases by contact with the oxygen present in the treating vessel.

It will be desirable to employ an amount of oxidizing agent at least equivalent to the theoretical amount required to sweeten. The invention has been described and exem- 10 plified-by employment of 0.5 to 1.0% by volume of the catalytic alkali metal hydroxide solution. It is contemplated that as little as 0.1 and as much as 5% by volume, or more, of the alkali metal hydroxide solution. based on the sour naphtha, may be employed. Very good results, however, are obtained with 1% by volume and this amount may be preferred.

The nature and objects of the present invention having been completely described and illustrated,

what I wish to claim as new and useful and to secure by Letters Patent is:

l. A method for sweetening a sour petroleum distillate containing mercaptans and having a final boiling point no greater than 750 P. which comprise adding to said distillate a small but effective catalytic amount of a benzenoid compound selected from the group consisting of the amines and phenols and then contacting the sour distillate containing the benzenoid compound with a catalytic amount no more than 5% by volume of a solution of an alkali metal hydroxide while adding a sufficient amount of a mild oxidiz ing agent to convert the mercaptans to disulfides and to obtain a sweetened distillate.

2. A method for sweetening asour petroleum distillate containing mercaptans and having a final boiling point no greater than 750 F. which comprises adding to said distillate an amount of a benzenoid compound selected from the group consisting of the amines and phenols in the range from 0.001 to 1.0 per cent by volume of said distillate, then contacting the sour distillate containing the benzenoid compound with a sodium hydroxide solution in an amount in the range between 0.1 and 5% by volume while adding a sufficient amount of air to convert the mercaptans to disulfides, and separating the contacted distillate from said sodium hydroxide solution to obtain a sweetened distillate.

3. A method for sweetening a sour petroleum distillate containing mercaptans and having a final boiling point no greater than-750 F. which comprises adding to said distillate a small but effective catalytic amount of a benzenoid compound selected from the group consisting of the amines and phenols, then contacting the sour distillate containing the benzenoid compound with a catalytic amount no more than 5% by volume of a solution of an alkali metal hydroxide while adding a sufficient amount of a mild oxidizing agent to convert the mercaptans to disulfides, separating the contacted distillate from said alkali metal hydroxide solution to obtain a sweetened distillate and contacting additional quantities of said sour distillate containing the benzenoid compound with said separated alkali metal hydroxide solution.

4. A method for sweetening a sour petroleum distillate containing mercaptans and having a final boiling point no greater than 750 F. which comprises adding to said distillate an amount of a benzenoid compound selected from the group consisting of the amines and phenols in the range from 0.001 to 1.0 per cent by volume of said distillate, then contacting the sour distillate containing the benzenoid compound with an amount in the range between 0.1 and 5% by volume of a sodium hydroxide solution while adding a suflicient amount of air to convert the mercaptans to disulfides, separating the contacted distillate from said sodium hydroxide solution to obtain a sweettitles of said sour distillate containing the hen- 1 1 1 2' zenoidcompoumi with said separated' sodium STATESPATENTS hydroxide solution. Numbr Name Date JOHN BROWDER' 2,341,878 Nixon Feb. 15, 1944- 2,425,414 Bond Aug; 12} 1947 REFERENCES CITED 5 2,457,975 B011, -Jan. 4', 1949' The following references are of record in the 2,462,870 erguson Feld. 22,1949 8' Ofthls Patent: 2,464,019 Bond t all Mail. 3, 1949 2,468,701 Caule'y' Aug. 26', I949 

1. A METHOD FOR SWEETENING A SOUR PETROLEUM DISTILLATE CONTAINING MERCAPTANS AND HAVING A FINAL BOILING POINT NO GREATER THAN 750* F. WHICH COMPRISES ADDING TO SAID DISTILLATE A SMALL BUT EFFECTIVE CATALYTIC AMOUNT OF A BENZENOID COMPOUND SELECTED FROM THE GROUP CONSISTING OF THE AMINES AND PHENOLS AND THEN CONTACTING THE SOUR DISTILLATE CONTAINING THE BENZENOID COMPOUND WITH A CATALYTIC AMOUNT NO MORE THAN 5% BY VOLUME OF A SOLUTION OF AN ALKALI METAL HYDROXIDE WHILE ADDING A SUFFICIENT AMOUNT OF A MILD OXIDIZ ING AGENT TO CONVERT THE MERCAPTANS TO DISULFIDES AND TO OBTAIN A SWEETENED DISTILLATE. 